patch 7.4.1557

Problem:    Windows cannot be identified.
Solution:   Add a unique window number to each window and functions to use it.

src/version.c

@@ -743,6 +743,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1557,
 /**/
     1556,
 /**/